Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disorder that targets the nerve cells controlling voluntary muscles. The disease causes the gradual deterioration of motor neurons in the brain and spinal cord, leading to muscle weakness, atrophy, and eventual paralysis. While physical activity is an important part of managing ALS, the goal shifts from achieving muscle hypertrophy, or growth, to preserving existing function and overall well-being.
The Physiology of Muscle Loss in ALS
Building new muscle is fundamentally limited in ALS because the disease attacks the communication system that triggers muscle growth. ALS causes the progressive loss of both upper and lower motor neurons. These motor neurons are the only way the brain can send signals to the muscle fibers, and their degeneration results in a process called denervation.
When a muscle fiber loses its connection to a motor neuron, it can no longer be activated and begins to waste away, a condition known as muscle atrophy. Surviving motor neurons may initially attempt to reinnervate orphaned muscle fibers to maintain strength. However, the relentless progression of the disease eventually overwhelms this compensatory effort, leading to widespread and irreversible muscle loss.
Traditional muscle building involves creating microscopic tears through resistance exercise, which requires a robust signal from intact motor neurons. This process is precisely what ALS compromises. For individuals with ALS, intense exercise that causes muscle breakdown is counterproductive and may hasten muscle fatigue, as remaining motor units are already working near their maximal capacity.
Realistic Goals for Physical Activity
Given the physiological limitations imposed by motor neuron loss, the focus of physical activity shifts away from muscle gain toward maintenance and symptom management. The primary goal is to preserve functional independence for as long as possible. This includes maintaining strength in unaffected or less-affected muscles to compensate for areas of weakness.
Regular, gentle movement helps maintain the range of motion in joints, preventing stiffness and painful contractures that arise from immobility. Activity also manages secondary symptoms, such as reducing muscle spasticity and improving circulation. Exercise provides psychological benefits, promoting better sleep, enhancing mood, and improving overall quality of life.
Physical activity is a therapeutic tool intended to slow the rate of decline and manage daily challenges, rather than a method to reverse the underlying pathology. The intention is to keep the body in the best possible condition to support daily activities, not to increase physical capacity beyond the disease’s natural limits.
Recommended Types of Movement and Safety Limits
Physical activity for a person with ALS should always be tailored and approved by a physician, ideally in consultation with a physical therapist specializing in neuromuscular diseases. Recommended activities fall into three main categories: light aerobic exercise, gentle stretching, and low-level resistance training. Light aerobic activities, such as walking, stationary cycling, or water-based therapy, maintain cardiovascular health and endurance without overstressing muscles.
Gentle stretching and range-of-motion exercises are important for joint mobility and comfort. These movements should be slow and performed without pain, holding the stretch for 30 to 60 seconds to maintain soft tissue flexibility and prevent shortening of muscles and tendons. Low-level resistance training may be appropriate for muscles that still have some strength, typically using light weights, resistance bands, or body weight.
The most important safety guideline is strictly avoiding overexertion, which can lead to “overwork weakness.” Individuals must stop exercising immediately if they feel fatigue, pain, or muscle discomfort. A good measure of appropriate intensity is a quick recovery, meaning any exercise-induced fatigue or soreness should resolve within 30 to 60 minutes and not carry over into the next day. Monitoring for signs like muscle twitching or excessive shortness of breath is important, and patients may benefit from inspiratory muscle training to support respiratory function.